Like zaG sez, run pipe insulation around the rails. You can get it at Lowe's or Ace Hardware.
Run the insulation around the rails. You can also put a layer of bubble wrap on the deck and bottom. You can get bubble wrap at Kinko's. Once the board is encapsulated in plastic, slip it into a board sock. Repeat this process with all of the boards you are traveling with. When you put the wrapped and socked boards into the big board bag, stuff all the voids with beach towels and clothing to keep the load from shifting .
Be sure to check your airlines weight and dimension limits before you pack and expect tthe TSA Nazis to unzip and search your boardbag.